Countenance a false start by the winner (4)
I believe the answer is:
face
'countenance' is the definition.
(I know that face is a type of countenance)
'a false start by the winner' is the wordplay.
'start' indicates taking the first letters.
'by' is a charade indicator (letters next to each other).
'the winner' becomes 'ace'.
The initial letter of 'false' is 'f'.
'f'+'ace'='FACE'
(Other definitions for face that I've seen before include "Cope with" , "celebrity" , "TV show" , "Outward appearance" , "Front -- confront" .)